What data type does php query the database to return?

The data types returned by php querying the database are: 1. Array type. Each element in the array represents a record in the database, and the key name of each element corresponds to the field name; 2. Object type, through Object accessor to get and set the attributes of the class; 3. For integer and floating point types, you can use queries like "SELECT COUNT(*) FROM table"; 4. For Boolean types, you can use "SELECT field1 FROM table WHERE field2 = ' value'"query.

The operating environment of this article: Windows 10 system, php8.1.3 version, dell g3 computer

In the process of using PHP to query the database, we It is often necessary to understand the data type returned by the query results so that the data can be better processed and used. PHP can use various methods and functions to query the database, but no matter which method is used, the query results will return certain data types. This article will give you a detailed introduction to the data types returned by PHP querying the database.

1. Array type

In PHP, one of the most common data types is array. When we query the database using a SQL statement similar to "SELECT * FROM table", the query results will be encapsulated into an array. Each element in the array represents a record in the database, where the key name of each element corresponds to the field name, and the corresponding key value is the value corresponding to the field. For example:

$conn = mysqli_connect($host, $user, $password, $database);
$result = mysqli_query($conn, "SELECT * FROM table");
$rows = array();
while($row = mysqli_fetch_assoc($result)) {
    $rows[] = $row;
}
print_r($rows);

The above code encapsulates the query results into a two-dimensional array, where each one-dimensional array represents a record in the database. The key name of the array is the same as the field name in the database, and the corresponding key value is the value of this field.

2. Object type

In addition to array types, query results can also be encapsulated into object types. The main benefit of using object types is that you can get and set class properties through object accessors. For example:

$conn = mysqli_connect($host, $user, $password, $database);
class Record {
    public $field1;
    public $field2;
}
$result = mysqli_query($conn, "SELECT * FROM table");
$rows = array();
while($row = mysqli_fetch_object($result, Record::class)) {
    $rows[] = $row;
}
print_r($rows);

The above code encapsulates the query result into a Record class object. The attribute name of the object is the same as the field name in the database, and the corresponding attribute value is the value of the field.

3. Integer and floating point types

When we use a SQL statement similar to "SELECT COUNT(*) FROM table" to query the database, the query result will be Returns an integer value representing the number of records matching the query criteria. Similarly, when we use aggregate functions such as SUM, AVG, etc., the query result will also return a floating point value, which represents the statistical information of the query results. For example:

$conn = mysqli_connect($host, $user, $password, $database);
$result = mysqli_query($conn, "SELECT COUNT(*) FROM table");
$count = mysqli_fetch_row($result);
echo "Total rows: " . $count[0];

The above code encapsulates the query result into an integer value, which represents the number of records matching the query conditions.

4. Boolean type

When we query the database using a SQL statement similar to "SELECT field1 FROM table WHERE field2 = 'value'", the query results will be returned A Boolean value indicating whether the specified value value exists in field field2. For example:

$conn = mysqli_connect($host, $user, $password, $database);
$result = mysqli_query($conn, "SELECT field1 FROM table WHERE field2 = 'value'");
if(mysqli_num_rows($result) > 0) {
    echo "Value exists.";
} else {
    echo "Value does not exist.";
}

The above code encapsulates the query result into a Boolean value, which indicates whether the specified value value exists in field field2.

Summary:

The above are several data types returned by PHP query database, including array type, object type, integer type, floating point type and Boolean type. To flexibly use the data types in the query results, you can perform data conversion and type judgment as needed.

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